Method for Manufacturing a Resin Fiber and Nozzle Head and Manufacturing Device Used in Same

ABSTRACT

Provided is a method for manufacturing a resin fiber capable of increasing a production volume based on high operability, and a nozzle head and a manufacturing device used in the same. The method for manufacturing a resin fiber is a method for manufacturing a resin fiber that is a long ultrafine fiber obtained by stretching a thermoplastic resin by a high-pressure gas flow. A gas flow from a high-pressure gas ejection port applies a negative pressure to a discharge port, externally extracting and emitting a molten resin inside the discharge port into the air while stretching the molten resin, and stretching while cooling the molten resin. The manufacturing device comprises an extruder that extrudes a molten resin from a nozzle on a tip of a barrel while melting the resin using a screw in the barrel, and a nozzle head attached to a tip of the nozzle. The nozzle head is provided with a discharge port and a high-pressure gas ejection port on a substantially vertical face. The discharge port extrudes the molten resin, and the high-pressure gas ejection port is provided near the discharge port and forms a substantially horizontal gas flow so that the molten resin inside the discharge port is externally extracted and emitted into the air while stretched. The discharge port has a diameter set to 0.5 mm or greater.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a method for manufacturing a resin fiber in which an extruded thermoplastic resin is stretched by high-pressure gas to form an aggregate of long fibers, and a nozzle head and a manufacturing device used in the same, and particularly relates to a method for manufacturing a resin fiber comprising an aggregate of long ultrafine fibers having a diameter in the nano-order, a manufacturing device, and a nozzle head used in the same.

Description of the Background Art

A resin fiber comprising an aggregate of long ultrafine fibers having a diameter of several microns to sub-microns is used in various filters and non-woven fabrics. While an electrospinning method has been proposed from long ago as a method for manufacturing such a resin fiber, in recent years many studies have been conducted on a melt-blowing method due to the enhanced productivity and safety thereof. In such a melt-blowing method, a thermoplastic resin extruded from an extruder is emitted into the air by blowing high-pressure gas using a nozzle part, forming an aggregate of long fibers (refer to Non-Patent Document 1).

For example, Patent Document 1 discloses a method for manufacturing a resin fiber comprising an aggregate of long ultrafine polypropylene fibers based on a melt-blowing method. In Example 2 thereof, a tip of a center discharge port through which a molten resin is extruded is surrounded by a hot air blowout port, the molten resin is stretched while the melted state of the resin is maintained inside a hot air converging cylindrical part extending downstream, the resin is emitted from an opening into the air, and an aggregate of long fibers is collected by a collecting part disposed in a horizontal direction. Here, while a diameter of the center discharge port should be 0.1 to 0.2 mm, with the melted state for stretching the resin in the hot air converging cylindrical part being controlled, it is stated that, depending on the inner diameter or adjustment of the temperature of the interior, discharge is no longer possible or only ultrafine fibers of a micron-order can be obtained.

Furthermore, Patent Document 2 also discloses a method for manufacturing a resin fiber comprising an aggregate of long ultrafine thermoplastic resin fibers based on a melt-blowing method. A plurality of small molten resin spray ports is provided around a most-expanded diameter opening through which a gas heated to a temperature higher than the temperature of a molten resin is sprayed outside the device in a horizontal direction, and a molten resin sprayed upon pressurization is engulfed in a flow of a gas sprayed from a gas spray port and then sprayed outside the device from the most-expanded diameter opening, stretching the molten resin in the spraying direction. Here, as one example, Patent Document 2 describes a 3-mm tube diameter of the molten resin spray port being decreased to 0.4 mm to apply pressure, and a gas being sprayed from the gas spray port having a 2-mm diameter and then ejected outside the device from the most-expanded diameter opening having a 22-mm diameter.

PATENT DOCUMENTS Non-Patent Documents

-   Non-Patent Document 1: Kunihiro Shinji, “Nanofiber no Sekai (The     World of Nanofibers)”, Japan Electrical Insulating and Advanced     Performance Materials Industrial Association, Denzai Journal, No.     626, 2015.5, PP.16-18

Patent Documents

-   Patent Document 1: Japanese Laid-Open Patent Application No.     2013-185272 -   Patent Document 2: Japanese Laid-Open Patent Application No.     2016-23399

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

In a method for manufacturing long ultrafine thermoplastic resin fiber based on a melt-blowing method, the resin is stretched, decreasing the diameter thereof. While the production volume can be increased based on high operability by safely controlling such a resin stretching step, in Patent Document 1 the hot air converging cylindrical part is provided in order to isolate the stretching step from the outside, and in Patent Document 2 a high-temperature gas flow having a heat capacity greater than a capacity of the resin is formed and the resin is sprayed therein, isolating the sprayed resin from the outside.

The present invention was made in light of such circumstances, and it is therefore an object of the present invention to provide a method for manufacturing a resin fiber capable of significantly increasing a production volume based on high operability, and a nozzle head and a manufacturing device used in the same.

Means for Solving the Problems

A method for manufacturing a resin fiber according to the present invention is a method for manufacturing a resin fiber that is a long ultrafine fiber obtained by stretching a thermoplastic resin by a high-pressure gas flow, the method comprising the steps of applying a negative pressure of a gas flow from a high-pressure gas ejection port provided near a discharge port through which a molten resin is extruded to the discharge port, externally extracting the molten resin inside the discharge port, and emitting the molten resin into the air while stretching the molten resin.

According to such an invention, while the molten resin is extracted and stretched into a long ultrafine fiber by a negative pressure resulting from the gas flow, it is easy to stabilize operation, achieve high operability, and increase the extruded amount by simply adjusting the gas flow in accordance with the extruded amount of resin, making it possible to significantly increase the production volume based on high operability.

In the invention described above, the molten resin that remains inside the discharge port may be externally extracted and stretched by a negative pressure even when the molten resin extruded from the discharge port is supplied from an extruder and the supply of the molten resin from the extruder is stopped. According to such an invention, it is possible to reliably extract and stretch the molten resin into a long ultrafine fiber by the negative pressure resulting from the gas flow from the high-pressure gas ejection port.

In the invention described above, the discharge port may have a diameter that decreases a flow resistance of the molten resin so that the molten resin can be extracted by the negative pressure resulting from the gas flow. Further, in the invention described above, the diameter of the discharge port may be 0.5 mm or greater. According to such an invention, it is possible to reliably extract and stretch the molten resin into a long ultrafine fiber by the negative pressure resulting from the gas flow from the high-pressure gas ejection port, and further increase the production volume.

Furthermore, a manufacturing device of a resin fiber according to the present invention is a manufacturing device of a resin fiber that is a long ultrafine fiber obtained by stretching a thermoplastic resin by a high-pressure gas flow, comprising an extruder that extrudes a molten resin from a nozzle on a tip of a barrel while melting the resin using a screw in the barrel, and a nozzle head attached to a tip of the nozzle. The nozzle head is provided with a plurality of pairs of a discharge port that extrudes the molten resin and a high-pressure gas ejection port that is near the discharge port and forms a substantially horizontal gas flow, on a substantially vertical face. The high-pressure gas ejection port is positioned near the discharge port and the discharge port has a diameter set to 0.5 mm or greater so that the molten resin inside the discharge port is externally extracted and emitted into the air while stretched.

According to such an invention, it is possible to extract and stretch the molten resin into a long ultrafine fiber by the negative pressure resulting from the gas flow, stabilize operation, achieve high operability, and increase the extruded amount by simply adjusting the amount of the gas flow in accordance with the extruded amount of resin, and thus significantly increase the production volume.

In the invention described above, the plurality of pairs may be provided on the face along a horizontal line. Further, in the invention described above, the high-pressure gas ejection ports of the plurality of pairs may be provided so that the respective axes are mutually spread into a fan shape toward an ejection direction. According to such an invention, the production volume can be further increased based on high operability.

Furthermore, a nozzle head according to the present invention is a nozzle head used in an extruder that extrudes a molten resin from a nozzle on a tip of a barrel while melting the resin using a screw in the barrel in a manufacturing device of a resin fiber that is a long ultrafine fiber obtained by stretching a thermoplastic resin by a high-pressure gas flow, and attached to a tip of the nozzle. The nozzle head is provided with a plurality of pairs of a discharge port that extrudes the molten resin and a high-pressure gas ejection port that is near the discharge port and forms a substantially horizontal gas flow, on a substantially vertical face when attached to the manufacturing device. The high-pressure gas ejection port is positioned near the discharge port and the discharge port has a diameter set to 0.5 mm or greater so that the molten resin inside the discharge port is externally extracted and emitted into the air while stretched.

According to such an invention, the nozzle head is attached to a manufacturing device of a resin fiber, making it possible to extract and stretch the molten resin into a long ultrafine fiber by the negative pressure resulting from the gas flow, stabilize operation, and achieve high operability by simply adjusting the amount of gas flow in accordance with the extruded amount of resin. Further, the extruded amount is increased, making it possible to significantly increase the production volume.

In the invention described above, the plurality of pairs may be provided on the face so as to extend along the horizontal line when the nozzle head is attached to the manufacturing device. Further, in the invention described above, the high-pressure gas ejection ports of the plurality of pairs may be provided so that the respective axes are mutually spread into a fan shape toward the ejection direction. According to such an invention, the production volume can be further increased based on high operability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view (partial block diagram) of a main portion of a manufacturing device of a resin fiber in one example according to the present invention.

FIGS. 2A and 2B are a front view and a side cross-sectional view of a nozzle head, respectively.

FIGS. 3A and 3B are top cross-sectional views of a nozzle head.

FIG. 4 is a scanning electron microscope (SEM) image of a resin fiber manufactured by the manufacturing device of a resin fiber.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A manufacturing device of a resin fiber will now be described as one example according to the present invention using FIGS. 1 to 4.

As illustrated in FIG. 1, a manufacturing device 9 of a resin fiber is a manufacturing device of a resin fiber that is a long ultrafine fiber obtained by stretching a thermoplastic resin by a high-pressure gas flow, and includes an extruder 1 that extrudes a melted resin from a nozzle 2 a, and a nozzle head 10 attached to a tip of the nozzle 2 a.

The extruder 1 includes a barrel 2 and a screw 3 that knead and transport a raw material such as a pellet made from a thermoplastic resin toward the nozzle 2 a while heating and melting the raw material, and a hopper 4 for supplying the raw material to an interior of the barrel 2. Further, the barrel 2 comprises a heater 5 on an outer periphery thereof, making it possible to heat the interior. The nozzle head 10 for discharging a resin is fixed to the tip of the nozzle 2 a provided in an extrusion direction of the resin of the barrel 2. The nozzle head 10 is configured so as to be connected to a gas heating part 7 by piping or the like, and a high-pressure gas supplied from a gas supply part 6 such as a gas compressor connected to an end thereof is heated and then supplied. The gas heating part 7 can comprise a heating part such as a heater around a gas pressure-feeding tube, for example.

As illustrated in FIGS. 2A and 2B, the nozzle head 10 includes an attaching part 19 on an outer peripheral side for attaching the nozzle head 10 to the extruder 1, and a face part 11 on a center side where a main surface is disposed substantially vertically (a normal line of the main surface is directed horizontally) when the nozzle head 10 is attached to the extruder 1. The attaching part 19 comprises a bolt hole or the like (not illustrated) for fixing the nozzle head 10 to the extruder 1. Further, the face part 11 is provided so as to protrude in an extrusion direction of the resin with respect to the attaching part 19.

The face part 11 is further provided with a discharge port 12 that discharges a resin, and a gas ejection port 13 that ejects high-pressure gas. The discharge port 12 and the gas ejection port 13 form a pair with one of each disposed near each other. In this example, a plurality of pairs of the discharge port 12 and the gas ejection port 13 are provided. Providing such a plurality of pairs can improve the production volume of resin fiber per unit time, and is thus preferred.

The discharge port 12 communicates with a resin inflow chamber 16. The resin inflow chamber 16 is positioned in the extrusion direction of the resin with respect to the nozzle 2 a of the barrel 2 when the nozzle head 10 is attached to the extruder 1, thereby forming a flow path of the melted resin supplied from the nozzle 2 a and making it possible to guide the melted resin to the discharge ports 12. The resin inflow chamber 16 is separated by a partition 15 from a gas inflow chamber 14 that forms a gas flow path. The gas inflow chamber 14 is connected to the gas ejection ports 13, and to an inflow port 14a of a high-pressure gas guided from outside the nozzle head 10. It should be noted that the inflow port 14a is connected to the gas heating part 7 described above. As a result, the gas inflow chamber 14 can guide the entered high-pressure gas to the gas ejection ports 13. Further, the axis of the gas ejection port 13 is disposed substantially horizontally so that the gas flow is formed substantially in the horizontal direction by the ejected high-pressure gas. The discharge ports 12 are also each preferably disposed substantially in the horizontal direction in line with the orientation of the gas ejection port 13 that forms the pair.

The gas ejection port 13 is disposed near the discharge port 12 as described above. In particular, the gas ejection port 13 is disposed near the discharge port 12 so that the melted resin can be externally extracted from inside the discharge port 12 by the negative pressure generated by the formed gas flow, and emitted into the air while stretched. Further, an inner diameter of the discharge port 12 is set so that a flow resistance of the melted resin is decreased, and the resin is extracted from the interior by a negative pressure resulting from the gas flow. The flow resistance of the melted resin decreases as the size of the inner diameter is increased. For example, an inner diameter of an outlet section of the discharge port 12 (near the surface of the face part 11) is preferably 0.5 mm or greater. In this example, the inner diameter of the discharge port 12 is 1.0 mm, the inner diameter of the gas ejection port 13 is 1.5 mm, and the distance between the centers thereof is 1.75 mm.

It should be noted that, as long as the resin can be extracted by the negative pressure as described above, the gas ejection port 13 can be disposed in any direction, regardless if above, below, or next to the discharge port 12. In this example, pairs with the gas ejection port 13 disposed below the discharge port 12 are arranged in an upper row, and pairs with the gas ejection port 13 disposed above the discharge port 12 are arranged in a lower row on the face part 11.

As illustrated in FIGS. 3A and 3B, in the plurality of pairs of the discharge port 12 and the gas ejection port 13 arranged in the lower row on the face part 11, the axes of the gas ejection ports 13 are provided so as to be mutually spread into a fan shape toward the ejection direction (upward in the drawing) in a horizontal plane. For example, the axes of the gas ejection ports 13 on both ends overlap both radii of a center angle a having a fan shape enclosed by two radii and an arc, and the axes of the other ejection ports 13 are also disposed so as to pass through a center point where the two radii of the same fan shape intersect. Similarly, the axes of the discharge ports 12 are provided so as to be mutually spread into a fan shape toward the discharge direction. With such an arrangement, adjustments can be made so as to suppress excessive intertwining between the resin fibers extracted from the respective pairs and emitted into the air, making it possible to increase the discharge amount of resin per unit time and increase the production volume per unit time, and thus such an arrangement is preferred. The same applies to the plurality of pairs of the discharge port 12 and the gas ejection port 13 arranged in the upper row on the face part 11.

It should be noted that the other details of the extruder 1 are publicly known, and a description thereof is omitted. Further, the manufacturing device 9 suitably comprises a collecting part for collecting the emitted resin fiber.

With reference to FIG. 1 once again, when a resin fiber is manufactured by the manufacturing device 9, high-pressure gas heated by the gas supply part 6 and the gas heating part 7 is supplied to the nozzle head 10 and ejected from the gas ejection ports 13 to form a gas flow while the resin melted by the extruder 1 is supplied to the nozzle head 10 and discharged from the discharge ports 12. As a result, the gas flow from the gas ejection ports 13 applies a negative pressure to a frontward side of the discharge ports 12, causing the molten resin inside the discharge ports 12 to be externally extracted and emitted into the air while stretched into a long ultrafine fiber. That is, the resin fiber can be manufactured by one type of melt-blowing method in which the molten resin is emitted into the air and stretched while cooled. At this time, operation can be easily stabilized by making the extruded amount of the resin uniform and adjusting the amount of gas flow in accordance with the extruded amount.

In particular, a resin fiber is continuously manufactured for some time by simply supplying the high-pressure gas even if the supply of the melted resin from the extruder 1 is stopped during the manufacture of the resin fiber. That is, the resin that remains inside the discharge ports 12 is found to be reliably externally extracted and stretched by the negative pressure resulting from the gas flow from the gas ejection ports 13.

As shown in FIG. 4, the resin fiber manufactured by the manufacturing device 9 is found to be a long ultrafine fiber such as a so-called nanofiber that has a diameter of about the micron order to several hundred nanometers. Further, the resin fibers moderately intertwine, and short, divided fiber and particulate resin are substantially not produced.

Thus, according to the manufacturing device 9, it is possible to manufacture a resin fiber that is a long ultrafine fiber by extracting a resin melted in the discharge ports 12 and emitting the resin into the air by the negative pressure resulting from the gas flow from the gas ejection ports 13, and thus stretching while cooling the resin. The resin is thus extracted from the discharge ports 12, thereby making it possible to stabilize operation and achieve high operability by simply adjusting the amount of gas flow in accordance with the extruded amount of the resin from the extruder 1. As described above, even when a plurality of pairs of the discharge port 12 and the gas ejection port 13 is arranged or the like and the discharge amount of resin is increased, it is possible to significantly increase the production volume based on high productivity as long as the amount of gas flow is adjusted in accordance with the increase.

Further, while the manufacturing device 9 can manufacture a long ultrafine fiber such as a nanofiber, the inner diameter of the discharge port 12 is extremely large compared to the fiber diameter, and is set to 1 mm in this example as described above. That is, the diameter of the resin fiber manufactured by the manufacturing device 9 is considered to not be dependent on the diameter of the discharge ports 12, but rather dependent on a balance between the gas flow from the ejection ports 13 and the amount of resin supplied. That is, the flow rate and the negative pressure from the ejection ports 13 are adjusted by adjusting the amount of gas flow in accordance with the amount of melted resin to be supplied. As a result, it is considered that the amount of extracted resin is adjusted, and the diameter is adjusted by the relationship with the gas flow rate. A long ultrafine fiber having a preferred diameter can be manufactured by balancing the amount of gas flow in accordance with the amount of melted resin to be supplied. Thus, preferably the diameter of the discharge ports 12 is made relatively large to decrease the flow resistance of the melted resin and facilitate the extraction of such a molten resin as described above. Further, it is easy to increase the discharge amount of the resin by relatively increasing the diameter of the discharge ports 12, and further increase the production volume per unit time by adjusting the amount of gas flow in accordance with this increase.

It should be noted that the diameter of the discharge ports 12 is large, resulting in minimal clogging as well as extremely easy maintenance.

Further, the production volume per unit time can be increased by further increasing the number of pairs of the discharge port 12 and the gas ejection port 13 of the nozzle head 10 by providing, for example, three or more rows of a plurality of pairs on the face part 11.

While the above has described examples according to the present invention and modifications based on these, the present invention is not necessarily limited thereto. Further, those skilled in the art may conceive various alternative examples and modified examples without departing from the spirit or the appended claims of the present invention.

DESCRIPTIONS OF REFERENCE NUMERALS

-   10 Nozzle head -   11 Face part -   12 Discharge port -   13 Gas ejection port 

1. A method for manufacturing a resin fiber that is a long ultrafine fiber obtained by stretching a thermoplastic resin by a high-pressure gas flow, the method comprising the steps of: applying a negative pressure of a gas flow from a high-pressure gas ejection port provided near a discharge port through which a molten resin is extruded to the discharge port, externally extracting the molten resin inside the discharge port, and emitting the molten resin into the air while stretching the molten resin.
 2. The method for manufacturing a resin fiber according to claim 1, wherein the molten resin that remains inside the discharge port is externally extracted and stretched by a negative pressure even when the molten resin extruded from the discharge port is supplied from an extruder and the supply of the molten resin from the extruder is stopped.
 3. The method for manufacturing a resin fiber according to claim 1, wherein the discharge port has a diameter that decreases a flow resistance of the molten resin so that the molten resin can be extracted by the negative pressure resulting from the gas flow.
 4. The method for manufacturing a resin fiber according to claim 3, wherein the diameter of the discharge port is 0.5 mm or greater.
 5. A manufacturing device of a resin fiber that is a long ultrafine fiber obtained by stretching a thermoplastic resin by a high-pressure gas flow, comprising: an extruder that extrudes a molten resin from a nozzle on a tip of a barrel while melting a resin using a screw in the barrel; and a nozzle head attached to a tip of the nozzle; the nozzle head being provided with a plurality of pairs of a discharge port through which the molten resin is extruded, and a high-pressure gas ejection port that is near the discharge port and forms a substantially horizontal gas flow, on a substantially vertical face; and the high-pressure gas ejection port being positioned near the discharge port and the discharge port having a diameter set to 0.5 mm or greater so as to externally extract the molten resin inside the discharge port, and emit the molten resin into the air while stretching the molten resin.
 6. The manufacturing device of a resin fiber according to claim 5, wherein the plurality of pairs is provided on the face along a horizontal line.
 7. The manufacturing device of a resin fiber according to claim 6, wherein the high-pressure gas ejection ports of the plurality of pairs are provided so that respective axes thereof are mutually spread into a fan shape toward an ejection direction.
 8. A nozzle head used in an extruder that extrudes a molten resin from a nozzle on a tip of a barrel while melting a resin using a screw in the barrel in a manufacturing device of a resin fiber that is a long ultrafine fiber obtained by stretching a thermoplastic resin by a high-pressure gas flow, and attached to the tip of the nozzle, comprising: a plurality of pairs of a discharge port through which the molten resin is extruded, and a high-pressure gas ejection port that is near the discharge port and forms a substantially horizontal gas flow, on a substantially vertical face when the nozzle head is attached to the manufacturing device; the high-pressure gas ejection port being positioned near the discharge port and the discharge port having a diameter set to 0.5 mm or greater so as to externally extract the molten resin inside the discharge port, and emit the molten resin into the air while stretching the molten resin.
 9. The nozzle head according to claim 8, wherein the plurality of pairs is provided on the face so as to extend along a horizontal line when the nozzle head is attached to the manufacturing device.
 10. The nozzle head according to claim 9, wherein the high-pressure gas ejection ports of the plurality of pairs are provided so that respective axes thereof are mutually spread into a fan shape toward an ejection direction.
 11. The method for manufacturing a resin fiber according to claim 2, wherein the discharge port has a diameter that decreases a flow resistance of the molten resin so that the molten resin can be extracted by the negative pressure resulting from the gas flow.
 12. The method for manufacturing a resin fiber according to claim 11, wherein the diameter of the discharge port is 0.5 mm or greater. 